This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. In breast conservation surgery, the current method to locate non-palpable breast tumors is pre-operative image-guided wire placement localization. However, wire localization is unable to demarcate irregularly shaped tumors, and positive tumor margins, which require repeat surgeries, are discovered in many patients [1]. As an alternative to wire localization, we propose using MR-Image guided High Intensity Focused Ultrasound (MRgHIFU) to create thermal lesions which circumscribe a non-palpable breast tumor, providing an excision guide during breast conservation surgery. This study investigates visibility and palpability of HIFU lesions in cadaver breast tissue.